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Indexing labeled graphs for pattern matching is a central challenge of pangenomics. Equi et al. (Algorithmica, 2022) developed the Elastic Founder Graph ($\mathsf{EFG}$) representing an alignment of $m$ sequences of length $n$, drawn from…

Data Structures and Algorithms · Computer Science 2023-03-10 Nicola Rizzo , Massimo Equi , Tuukka Norri , Veli Mäkinen

We study the problem of matching a string in a labeled graph. Previous research has shown that unless the Orthogonal Vectors Hypothesis (OVH) is false, one cannot solve this problem in strongly sub-quadratic time, nor index the graph in…

Data Structures and Algorithms · Computer Science 2022-06-14 Massimo Equi , Tuukka Norri , Jarno Alanko , Bastien Cazaux , Alexandru I. Tomescu , Veli Mäkinen

We introduce a compact pangenome representation based on an optimal segmentation concept that aims to reconstruct founder sequences from a multiple sequence alignment (MSA). Such founder sequences have the feature that each row of the MSA…

Data Structures and Algorithms · Computer Science 2020-05-20 Veli Mäkinen , Bastien Cazaux , Massimo Equi , Tuukka Norri , Alexandru I. Tomescu

This paper shows the weighted matching problem on general graphs can be solved in time $O(n(m + n\log n))$ for $n$ and $m$ the number of vertices and edges, respectively. This was previously known only for bipartite graphs. The crux is a…

Data Structures and Algorithms · Computer Science 2016-11-24 Harold N. Gabow

In this paper, we give new, tight subexponential lower bounds for a number of graph embedding problems. We introduce two related combinatorial problems, which we call String Crafting and Orthogonal Vector crafting, and show that these…

Computational Complexity · Computer Science 2016-10-31 Hans L. Bodlaender , Tom C. van der Zanden

Exact pattern matching in labeled graphs is the problem of searching paths of a graph $G=(V,E)$ that spell the same string as the pattern $P[1..m]$. This basic problem can be found at the heart of more complex operations on variation graphs…

Computational Complexity · Computer Science 2020-06-04 Massimo Equi , Roberto Grossi , Veli Mäkinen

We prove essentially tight lower bounds, conditionally to the Exponential Time Hypothesis, for two fundamental but seemingly very different cutting problems on surface-embedded graphs: the Shortest Cut Graph problem and the Multiway Cut…

Computational Complexity · Computer Science 2021-02-18 Vincent Cohen-Addad , Éric Colin de Verdière , Daniel Marx , Arnaud de Mesmay

The run time complexity of state-of-the-art inference algorithms in graph-based dependency parsing is super-linear in the number of input words (n). Recently, pruning algorithms for these models have shown to cut a large portion of the…

Computation and Language · Computer Science 2016-06-09 Effi Levi , Roi Reichart , Ari Rappoport

We revisit the complexity of approximate pattern matching in an elastic-degenerate string. Such a string is a sequence of $n$ finite sets of strings of total length $N$, and compactly describes a collection of strings obtained by first…

Data Structures and Algorithms · Computer Science 2025-03-04 Paweł Gawrychowski , Adam Górkiewicz , Pola Marciniak , Solon P. Pissis , Karol Pokorski

Exact pattern matching in labeled graphs is the problem of searching paths of a graph $G=(V,E)$ that spell the same string as the given pattern $P[1..m]$. This basic problem can be found at the heart of more complex operations on variation…

Computational Complexity · Computer Science 2019-02-12 Massimo Equi , Roberto Grossi , Alexandru I. Tomescu , Veli Mäkinen

Let G be a directed graph with n vertices and non-negative weights in its directed edges, embedded on a surface of genus g, and let f be an arbitrary face of G. We describe a randomized algorithm to preprocess the graph in O(gn log n) time…

Data Structures and Algorithms · Computer Science 2013-05-13 Sergio Cabello , Erin Wolf Chambers , Jeff Erickson

For the first time we provide a succinct pattern matching index for arbitrary graphs that can be built in polynomial time, which requires less space and answers queries more efficiently than the one in [SODA 2021]. We show that, given an…

Data Structures and Algorithms · Computer Science 2021-11-09 Nicola Cotumaccio

Missing data imputation (MDI) is crucial when dealing with tabular datasets across various domains. Autoencoders can be trained to reconstruct missing values, and graph autoencoders (GAE) can additionally consider similar patterns in the…

Machine Learning · Computer Science 2022-10-20 Lev Telyatnikov , Simone Scardapane

An elastic-degenerate (ED) string is a sequence of $n$ sets of strings of total length $N$, which was recently proposed to model a set of similar sequences. The ED string matching (EDSM) problem is to find all occurrences of a pattern of…

Data Structures and Algorithms · Computer Science 2021-05-05 Giulia Bernardini , Paweł Gawrychowski , Nadia Pisanti , Solon P. Pissis , Giovanna Rosone

The directed acyclic word graph (DAWG) of a string $y$ of length $n$ is the smallest (partial) DFA which recognizes all suffixes of $y$ with only $O(n)$ nodes and edges. In this paper, we show how to construct the DAWG for the input string…

Data Structures and Algorithms · Computer Science 2023-07-06 Yuta Fujishige , Yuki Tsujimaru , Shunsuke Inenaga , Hideo Bannai , Masayuki Takeda

In the String Matching in Labeled Graphs (SMLG) problem, we need to determine whether a pattern string appears on a given labeled graph or a given automaton. Under the Orthogonal Vectors hypothesis, the SMLG problem cannot be solved in…

Data Structures and Algorithms · Computer Science 2025-08-05 Nicola Cotumaccio

Message-passing neural networks (MPNNs) are the leading architecture for deep learning on graph-structured data, in large part due to their simplicity and scalability. Unfortunately, it was shown that these architectures are limited in…

We study the problem of finding maximal exact matches (MEMs) between a query string $Q$ and a labeled graph $G$. MEMs are an important class of seeds, often used in seed-chain-extend type of practical alignment methods because of their…

Data Structures and Algorithms · Computer Science 2023-07-04 Nicola Rizzo , Manuel Cáceres , Veli Mäkinen

Let $G$ be an $n$-node and $m$-edge positively real-weighted undirected graph. For any given integer $f \ge 1$, we study the problem of designing a sparse \emph{f-edge-fault-tolerant} ($f$-EFT) $\sigma${\em -approximate single-source…

Data Structures and Algorithms · Computer Science 2016-01-22 Davide Bilò , Luciano Gualà , Stefano Leucci , Guido Proietti

In this paper, we extend the notion of gapped strings to elastic-degenerate strings. An elastic-degenerate string can been seen as an ordered collection of k > 1 seeds (substrings/subpatterns) interleaved by elastic-degenerate symbols such…

Data Structures and Algorithms · Computer Science 2016-10-27 Costas Iliopoulos , Ritu Kundu , Solon Pissis
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